How do I make a missile that lands with the nose facing down in BGE?
Since your question is not 100% clear, I assume the following:


You are using rigid body physics on your rocket object
You want to point the "nose" of the rocket in the direction in which it is travelling


I did not find a solution with logic bricks to solve point 2, but a few pieces of python code in an old Blender Artist thread (see below 1), which did the job. My minimal example looks like this (*blend below):





It contains an Empty ("spawner"), which spits out the Rocket object (on layer 2) with rigid body physics with a certain velocity in the spawners Y-Axis, triggered by the SPACE Key. The rockets "Nose" is it's Y axis, as seen in the upper part of the screenshot. The python snippet attached to the rocket object now turns the Y axis (second argument of alignAxisToVect) in the direction of motion in every frame. In my example the rocket gets deleted on contact with the Plane object. 

Update: The attached *blend uses rigid body physics on the rocket and convex hull collision bounds. This can be simplified to "dynamic" and "box" respectively, so the physics engine has less work to do. 

Enjoy!

1 https://blenderartists.org/forum/archive/index.php/t-246103.html